This invention relates to an inverse differential fill-up casing cementing float valve used in the cementing of casing in offshore oil and gas wells.
When running large diameter well casing from offshore drilling rigs into an open well bore to be cemented therein, strong sea currents may be encountered which may force the well casing away from its desired placement point in the open well bore in the sea floor. Since the well casing is usually of a large diameter and the well casing string of substantial length, as well as being buoyant, the ocean currents may push the casing far enough from the open well bore to create a problem.
To overcome this problem the well casing is filled with drilling mud with the drilling mud being kept inside the casing until the casing has been successfully guided into the open well bore. By filling the well casing with drilling mud during this process, the drilling mud inside the casing adds to the mass and weight of the casing string thereby making it more difficult for the ocean currents to displace or move the casing string.